@@ -1833,7 +1833,7 @@ def default_urllib3_manager( # noqa: C901
if proxy_server is None:
for proxyname in ("https_proxy", "http_proxy", "all_proxy"):
proxy_server = os.environ.get(proxyname)
- if proxy_server is not None and proxy_server != "":
+ if proxy_server:
break
if config is not None: